1. Field
The present invention relates generally to communications, and more specifically, to transmitting multi-cast broadcasts in wireless communication systems.
2. Background
The field of wireless communications has many applications including, e.g., cordless telephones, paging, wireless local loops, personal digital assistants (PDAs), Internet telephony, and satellite communication systems. A particularly important application is cellular telephone systems for mobile subscribers. As used herein, the term “cellular” system encompasses both cellular and personal communications services (PCS) frequencies. Various over-the-air interfaces have been developed for such cellular telephone systems including, e.g., frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). In connection therewith, various domestic and international standards have been established including, e.g., Advanced Mobile Phone Service (AMPS), Global System for Mobile (GSM), and Interim Standard 95 (IS-95). IS-95 and its derivatives, IS-95A, IS-95B, ANSI J-STD-008 (often referred to collectively herein as IS-95), and proposed high-data-rate systems are promulgated by the Telecommunication Industry Association (TIA) and other well known standards bodies.
Cellular telephone systems configured in accordance with the use of the IS-95 standard employ CDMA signal processing techniques to provide highly efficient and robust cellular telephone service. Exemplary cellular telephone systems configured substantially in accordance with the use of the IS-95 standard are described in U.S. Pat. Nos. 5,103,459 and 4,901,307, which are assigned to the assignee of the present invention and incorporated by reference herein. An exemplary system utilizing CDMA techniques is the cdma2000 ITU-R Radio Transmission Technology (RTT) Candidate Submission (referred to herein as cdma2000), issued by the TIA. The standard for cdma2000 is given in the draft versions of IS-2000 and has been approved by the TIA and 3GPP2. Another CDMA standard is the W-CDMA standard, as embodied in 3rd Generation Partnership Project “3 GPP”, Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214.
The telecommunication standards cited above are examples of some of the various communications systems that can be implemented to transmit voice and/or data. Within these systems, multiple users must share limited system resources. One such limitation is the availability of channels to support multiple users. For example, in a CDMA-type system, each user within the range of a base station is assigned one or more channels to conduct communications with the base station. If there were not enough channels, then a new user that is entering the range of the base station would be blocked from accessing the services of that base station.
In certain situations, it is desirable to transmit the same data to several users. This is particularly desirable for applications that incur a large load on the wireless network, such as video streaming. However, cellular base stations are presently configured to transmit the data on separate channels to each user, regardless of the similarity of the data to each user. Hence, it could be said that the base station is wasting channel resources every time the base station makes multiple transmissions with the same data content. There is a present need in the art for a method and apparatus for transmitting identical or similar data to multiple users without using multiple channels.